So, I get this email inviting me to join this organization, which claims it is an international honour society (note the spelling of honor... with the international u.) So I'm wondering if this society is legitimate and debating whether or not I should join it.

Thing is, the "honors" section of my application is rather desolate and it could use the friendly company of a few fillers. In the past I've turned down many invitations to join various honor societies, because I normally view such organizations as either baseless scams (a la "Who's Who Among American High School Students) or elitist cliques. But now, it's beginning to look rather attractive, having something like "Golden Key Honor Student" written next to my name. Of course, I do have a value system where I genuinely believe that the greatest honors are the ones that go unspoken for, and that being human, alone, is a condition that has much to do with this. The hero is the man who does his civic duty, quietly and without accolade, like the man who picks up littered trash at a park and deposits it in the appropriate garbage receptacle.

At any rate, I turn to you now for the following:
a.) is this group (Golden Key Int. Hon. Soc) legit?
b.) should I join it?

it's right up there with the "National Dean's List." If you've got a GPA over 3.6 or something like that, you'll hear from them. The only honor society I joined was because I wanted to apply for the scholarships they offered. I don't feel like paying an entry fee or going to any ceremonies.

If you're going to be active in an organization, then it might be a worthwhile endeavor.